ABC News has learned that Pakistani officials now believe that al Qaeda's master bomb maker and chemical weapons expert was one of the men killed in last week's U.S. missile attack in eastern Pakistan.
Midhat Mursi, 52, also known as Abu Khabab al-Masri, was identified by Pakistani authorities as one of four known major al Qaeda leaders present at an apparent terror summit in the village of Damadola early last Friday morning.
The United States had posted a $5 million reward for Mursi's capture. He is described by authorities as the man who ran al Qaeda's infamous Derunta training camp in Afghanistan, where he used dogs and other animals as subjects for experiments with poison and chemicals. His explosives training manual is still regarded as the bible for al Qaeda terrorists around the world.
"He wants to cause mayhem, major death, and he puts his expertise on the line. So the fact that we took him out is significant," said former FBI agent Jack Cloonan, an ABC News consultant, who was the senior agent on the FBI's al Qaeda squad. "He's the man who trained the shoe bomber Richard Reid and Zacarias Moussaoui, as well as hundreds of others."
Pakistani officials also said that Khalid Habib, the al Qaeda operations chief for Pakistan and Afghanistan, and Abdul Rehman al Magrabi, a senior operations commander for al Qaeda, were killed in the Damadola attack. Magrabi, sources told ABC News, was the son-in-law of Ayman al-Zawahiri, al Qaeda's No. 2 man.
Authorities tell ABC News that the terror summit was called to funnel new money into attacks against U.S. forces in Afghanistan.
"Pakistani intelligence says this was a very important planning session involving the very top levels of al Qaeda as they get ready for a new spring offensive," explained Alexis Debat, a former official in the French Defense Ministry and now an ABC News consultant
As for Zawahiri, U.S. and Pakistani officials agree that it is still possible but increasingly unlikely that he was killed. If he is alive, he has lost many of those close to him, however.
"Zawahiri, if he slept three hours on a normal night, he's sleeping an hour and a half right now with his eyes wide open," Cloonan said. "He's looking around right now and wondering who handed him up. Not a nice feeling."
ABC News' Chris Isham and Jill Rackmill contributed to this report.